Fspy add-on not installing
TLDR; Download the latest release: https://github.com/stuffmatic/fSpy-Blender/releases

Scroll down the github page and read the instructions on how to install the add-on properly:

Download the latest version from the release page (fSpy-Blender-VersionNumber.zip)
In Blender go to Edit &gt; User Preferences &gt; Add-ons and click Install from File
Select the fSpy-Blender-VersionNumber.zip file by using the file browser
Don't forget to enable the Add-on

If successfully enabled, a new menu entry in File &gt; Import will appear:


Don't download the entire repository!

Again, download the latest release: https://github.com/stuffmatic/fSpy-Blender/releases